The "Hudson Bay" is a great ride. If you like a relaxing train trip this is a good one. Two nights and a day to Churchill. Due to the tri-weekly schedule, you arrive in Churchill early in the morning, and depart that evening, or you have to stick around for a couple of days. A hotel is still advisable in Churchill because it's a very long day. Be sure to take one of the polar bear spotting trips.
The train is not fancy, but it has all the essentials: Sleeping car, diner/lounge, and best of all, VIA Rail Canada has excellent on board crews.